Nissan security indicator light 3

https://sierra-wiki.win/index.php/Understanding_the_Nissan_Ignition_ON_Light_and_Key_Symbol_on_Your_Dashboard

The Nissan security indicator light is a small LED on your key fob or dashboard that flashes to show the vehicle's anti-theft system is active. It's not something you notice every day, but it's quietly there, reassuring you that the car is locked and protected. If it stops blinking or behaves oddly, it might signal a battery issue or a system fault worth checking out.